U.S. patent application number 16/200058 was filed with the patent office on 2019-05-30 for organic light-emitting display device.
This patent application is currently assigned to LG DISPLAY CO., LTD.. The applicant listed for this patent is LG DISPLAY CO., LTD.. Invention is credited to Junseok BYUN, Dongyoung KIM, Yongbaek LEE.
Application Number | 20190165066 16/200058 |
Document ID | / |
Family ID | 65024791 |
Filed Date | 2019-05-30 |
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United States Patent
Application |
20190165066 |
Kind Code |
A1 |
LEE; Yongbaek ; et
al. |
May 30, 2019 |
ORGANIC LIGHT-EMITTING DISPLAY DEVICE
Abstract
An organic light-emitting display device includes pixels, a bank
that defines the pixels and has at least one hollow portion formed
between the pixels which neighbor each other, and a light stopper.
At least part of the light stopper is inserted into the hollow
portion.
Inventors: |
LEE; Yongbaek; (Paju-si,
KR) ; BYUN; Junseok; (Paju-si, KR) ; KIM;
Dongyoung; (Paju-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG DISPLAY CO., LTD. |
Seoul |
|
KR |
|
|
Assignee: |
LG DISPLAY CO., LTD.
Seoul
KR
|
Family ID: |
65024791 |
Appl. No.: |
16/200058 |
Filed: |
November 26, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/322 20130101;
H01L 51/5284 20130101; H01L 51/5253 20130101; H01L 27/326 20130101;
H01L 27/3246 20130101 |
International
Class: |
H01L 27/32 20060101
H01L027/32 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 29, 2017 |
KR |
10-2017-0161459 |
Claims
1. An organic light-emitting display device comprising: pixels: a
bank that defines the pixels and has at least one hollow portion
formed between the pixels which neighbor each other; and a light
stopper, at least part of which is inserted into the at least one
hollow portion.
2. The organic light-emitting display device of claim 1, wherein a
top surface of the light stopper is spaced a preset distance apart
from a top surface of the bank.
3. The organic light-emitting display device of claim 1, wherein
the at least one hollow portion has a shape of a hole that fully
penetrates an entire thickness of the bank.
4. The organic light-emitting display device of claim 1, wherein
the at least one hollow portion has a shape of a recess formed by
partially recessing a top surface of the bank inward.
5. The organic light-emitting display device of claim 1, wherein
the light stopper is selectively disposed between pixels that emit
light of different colors.
6. The organic light-emitting display device of claim 1, wherein
the pixels comprise: a first pixel that emits light of a first
color; a second pixel that neighbors the first pixel in a first
direction and emits light of a second color; and a third pixel that
neighbors the first pixel in a second direction and emits light of
the first color, wherein the light stopper is situated between the
first pixel and the second pixel but not between the first pixel
and the third pixel.
7. The organic light-emitting display device of claim 1, further
comprising: first electrodes allocated individually to the pixels;
an organic compound layer disposed on the first electrodes and
covering the pixels; and a second electrode disposed on the organic
compound layer and covering the pixels, wherein the organic
compound layer is physically separated on the bank in at least one
region where the light stopper is placed.
8. The organic light-emitting display device of claim 7, wherein
the second electrode is physically separated on the bank in the at
least one region.
9. The organic light-emitting display device of claim 1, further
comprising a barrier surrounding the light stopper.
10. The organic light-emitting display device of claim 9, wherein
the barrier is divided into a first portion and a second
portion.
11. The organic light-emitting display device of claim 10, wherein
the first portion and the second portion are made of different
materials.
12. The organic light-emitting display device of claim 9, wherein
the barrier includes an inorganic material.
13. The organic light-emitting display device of claim 1, wherein
the light stopper is black in color.
Description
[0001] This application claims the priority benefit of Korean
Patent Application No. 10-2017-0161459, filed on Nov. 29, 2017 in
the Republic of Korea, which is incorporated herein by reference
for all purposes as if fully set forth herein.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present disclosure relates to an organic light-emitting
display device.
Related Art
[0003] Recently, various display devices that are less bulky and
more lightweight than cathode ray tubes (CRTs) are being developed.
Examples of these display devices include liquid crystal displays
(LCDs), field emission displays (FEDs), plasma display panels
(PDPs), organic light-emitting display devices (OLEDs), etc.
[0004] Among these display devices, organic light-emitting displays
are self-emission displays that emit light through excitation of
organic compounds. In contrast to LCDs, the organic light-emitting
displays work without a backlight. Thus, the organic light-emitting
displays have advantages of a thin profile, lightness in weight,
and a simpler manufacturing process. Also, the organic light
emitting displays are widely used because they can be manufactured
at low temperatures, have a fast response time of 1 ms or less, and
feature low power consumption, wide viewing angle, and high
contrast.
[0005] An organic light-emitting display comprises pixels each
having an organic light-emitting diode that converts electrical
energy into light energy. The organic light-emitting diode
comprises an anode, a cathode, and an organic compound layer
situated between the anode and cathode. Holes and electrons are
injected from the anode and cathode, respectively, and they
recombine to form excitons, whereby the organic light-emitting
display displays an image when the excitons fall from the excited
state to the ground state.
[0006] The organic compound layer can comprise red (R), green (G),
and blue (B) organic compound layers. They can be formed to
correspond to red (R), green (G), and blue (B) pixels,
respectively. A fine metal mask (FMM) is typically used to pattern
the red (R), green (G), and blue (B) pixels. However, even with the
dramatic advances in the processing technology, there are
limitations in using the FMM to make high-resolution displays. As a
matter of fact, when the FMM is used to realize the resolution
above 1,000 PPI, it is currently hard to achieve a process yield of
more than a certain level.
[0007] Moreover, in order to implement a large-area high-resolution
display device, a large-area FMM mask corresponding thereto is
required. However, the larger the area of the mask, the more the
center will sag under the weight, which leads to various defects
such as displacement of the organic compound layer.
SUMMARY OF THE INVENTION
[0008] The present disclosure provides an organic light-emitting
display that improves display quality by minimizing color mixing
defects, and which addresses the limitations and disadvantages
associated with the related art.
[0009] In one aspect, there is provided an organic light-emitting
display device comprising pixels, a bank that defines the pixels
and has at least one hollow portion formed between the pixels which
neighbor each other, and a light stopper, at least part of which is
inserted into the hollow portion.
[0010] The top surface of the light stopper can be spaced a preset
distance apart from the top surface of the bank.
[0011] The hollow portion can have the shape of a hole that fully
penetrates the entire thickness of the bank.
[0012] The hollow portion can have the shape of a recess formed by
partially recessing the top surface of the bank inward.
[0013] The light stopper can be selectively disposed between pixels
that emit light of different colors.
[0014] The pixels can include a first pixel that emits light of a
first color, a second pixel that neighbors the first pixel in a
first direction and emits light of a second color, and a third
pixel that neighbors the first pixel in a second direction and
emits light of the first color. The light stopper can be situated
between the first pixel and the second pixel but not between the
first pixel and the third pixel.
[0015] The organic light-emitting display device can further
comprise first electrodes allocated individually to the pixels, an
organic compound layer that disposes on the first electrodes and
covers the pixels, and a second electrode that is disposed on the
organic compound layer and covers the pixels. The organic compound
layer can be physically separated on the bank in at least one
region where the light stopper is placed. The second electrode can
be physically separated on the bank in the at least one region.
[0016] The organic light-emitting display device can further
comprise a barrier surrounding the light stopper. The barrier can
be divided into a first portion and a second portion. The first
portion and the second portion can be made of different materials.
The barrier can include an inorganic material. The light stopper
can be black in color.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated on and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention. In the drawings:
[0018] FIG. 1 is a block diagram of an organic light-emitting
display device according to the present disclosure;
[0019] FIG. 2 is a schematic diagram of a pixel shown in FIG.
1;
[0020] FIG. 3 is diagrams showing concrete examples of FIG. 2;
[0021] FIG. 4 is a cross-sectional view of a pixel of an organic
light-emitting display device according to the present
disclosure;
[0022] FIG. 5 is a view for explaining problems with the related
art;
[0023] FIG. 6 is a cross-sectional view schematically showing an
organic light-emitting display device according to a first
exemplary embodiment of the present disclosure;
[0024] FIG. 7 is a view for explaining the positional relationship
of a light stopper according to the present disclosure;
[0025] FIGS. 8 and 9 are views for explaining another advantage of
the first exemplary embodiment of the present disclosure;
[0026] FIG. 10 is a cross-sectional view schematically showing an
organic light-emitting display device according to a second
exemplary embodiment of the present disclosure; and
[0027] FIGS. 11A to 11D are views chronologically showing an
example of a barrier formation method according to the present
disclosure.
DESCRIPTION OF THE EMBODIMENTS
[0028] Hereinafter, exemplary embodiments of the present disclosure
will be described in detail with reference to the attached
drawings. Throughout the specification, like reference numerals
denote substantially like components. In describing the present
disclosure, a detailed description of known functions or
configurations related to the present disclosure will be omitted
when it is deemed that they can unnecessarily obscure the subject
matter of the present disclosure. In describing various exemplary
embodiments, descriptions of the same or like components will be
given in the beginning but omitted in other exemplary
embodiments.
[0029] Although terms including ordinal numbers such as "first" and
"second" can be used to describe various components, the components
are not limited by the terms. The terms are used only to
distinguish one component from other components.
[0030] FIG. 1 is a block diagram of an organic light-emitting
display device according to the present disclosure. All the
components of the organic light-emitting display device according
to all embodiments of the present disclosure are operatively
coupled and configured. FIG. 2 is a schematic diagram of a pixel
shown in FIG. 1. FIG. 3 is diagrams showing concrete examples of
FIG. 2. FIG. 4 is a cross-sectional view of a pixel of an organic
light-emitting display device according to the present disclosure.
FIG. 5 is a view for explaining problems with the related art.
[0031] Referring to FIG. 1, an organic light-emitting display
device 10 according to the present disclosure comprises a display
drive circuit and a display panel DIS.
[0032] The display drive circuit comprises a data drive circuit 12,
a gate drive circuit 14, and a timing controller 16 and writes
vides data voltages of an input image to the pixels PXL on the
display panel DIS. The data drive circuit 12 converts digital video
data RGB inputted from the timing controller 16 into analog
gamma-compensated voltages to generate data voltages. The data
voltages outputted from the data drive circuit 12 are supplied to
data lines D1 to Dm. The gate drive circuit 14 sequentially
supplies gate signals to gate lines G1 to Gn in synchronization
with the data voltages and selects pixels PXL from the display
panel DIS to write the data voltages to.
[0033] The timing controller 16 receives, from a host system 19,
timing signals such as a vertical synchronization signal Vsync, a
horizontal synchronization signal Hsync, a data enable signal DE,
and a main clock MCLK, and synchronizes the operation timings of
the data drive circuit 12 and gate drive circuit 14 with each
other. Data timing control signals for controlling the data drive
circuit 12 comprise a source sampling clock (SSC), a source output
enable signal (SOE), etc. Gate timing control signals for
controlling the gate drive circuit 14 comprise a gate start pulse
(GSP), a gate shift clock (GSC), a gate output enable signal (GOE),
etc.
[0034] The host system 19 can be any one of the following: a
television system, a set-top box, a navigation system, a DVD
player, a Blu-ray player, a personal computer PC, a home theater
system, and a phone system. The host system 19 comprises a
system-on-chip (SoC) having a scaler incorporated in it, and
converts digital video data RGB of an input image into a format
suitable for display on the display panel DIS. The host system 19
sends timing signals Vsync, Hsync, DE, and MCLK, along with the
digital video data, to the timing controller 16.
[0035] The display panel DIS can have various shapes. That is, the
plane of the display panel DIS can be rectangular or square, and
also can have various free-form shapes, such as a circle, an
ellipse, or a polygon.
[0036] The display panel DIS comprises red (R), blue (B), and green
(G) pixels PXL that emit light red (R), blue (B), and green (G)
light, respectively. If required, the display panel DIS can further
comprise pixels PXL that emit light of another color, such as white
(W). For ease of explanation, a description will be given below
with respect to a display panel DIS comprising red (R), blue (B),
and green (G) pixels PXL, for example.
[0037] The pixels PXL can have various shapes. For example, the
plane of the pixels PXL can have various shapes, such as circular,
elliptical, or polygonal. One of the pixels PXL can have a
different size and/or different planar shape from another. Each of
the pixels PXL comprises an organic light-emitting diode.
[0038] The organic light-emitting display according to the present
disclosure comprises an organic compound layer OL that emits white
light (W) and red (R), blue (B), and green (G) color filters, in
order to produce red (R), blue (B), and green (G) colors. That is,
the organic light-emitting display can produce red (R), green (G),
and blue (B) colors as the white light (W) emitted from the organic
compound layer OL passes through the red (R), blue (B), and green
(G) color filters corresponding to the red (R), green (G), and blue
(B) pixels PXL.
[0039] In the organic light-emitting display according to the
present disclosure, the organic compound layer OL emitting white
light (W) is made wide enough to cover most of the entire surface
of the panel, so there is no need to use FMM to allocate red (R),
blue (B), and green (G) organic compound layers OL to the
corresponding pixels PXL, respectively. Thus, the present
disclosure has the advantage of avoiding problems with the use of
the aforementioned FMM--for example, a decrease in process yield
associated with high resolution and an alignment error which causes
displacement of the organic compound layer OL.
[0040] Referring to FIG. 2, a plurality of data lines D and a
plurality of gate lines G intersect on the display panel DIS of
FIG. 1, and the pixels PXL are arranged in a matrix at the
intersections. Each of the pixels PXL comprises an organic
light-emitting diode OLED, a driving thin-film transistor DT that
controls the amount of current flowing through the organic
light-emitting diode OLED, and a programming part SC for setting
the gate-source voltage of the driving thin-film transistor DT.
[0041] The programming part SC can comprise at least one switching
thin-film transistor and at least one storage capacitor. The
switching thin-film transistor turns on in response to a gate
signal from a gate line G to apply a data voltage from a data line
D to one electrode of the storage capacitor. The driving thin-film
transistor DT adjusts the amount of light emitted from the organic
light-emitting diode OLED by controlling the amount of current
supplied to the organic light-emitting diode OLED depending on the
level of voltage stored in the storage capacitor. The amount of
light emitted from the organic light-emitting diode OLED is
proportional to the amount of current supplied from the driving
thin-film transistor DT. Such a pixel PXL is connected to a
high-level voltage source Evdd and a low-level voltage source Evss
to receive high-level power supply voltage and low-level power
supply voltage from a power generating part. The thin-film
transistors of the pixel PXL can be implemented as p-type or
n-type. Moreover, semiconductor layers of the thin-film transistors
of the pixel PXL can contain amorphous silicon, polysilicon, or
oxide. A description will be given below with respect to a
semiconductor layer that contains oxide. The organic light-emitting
diode OLED comprises an anode ANO, a cathode CAT, and an organic
compound layer sandwiched between the anode ANO and cathode CAT.
The anode ANO is connected to the driving thin-film transistor
DT.
[0042] As shown in (a) of FIG. 3, a subpixel can comprise an
internal compensation circuit CC, as well as the aforementioned
switching transistor SW, driving transistor DR, capacitor Cst, and
organic light-emitting diode OLED. The internal compensation
circuit CC can comprise one or more transistors connected to a
compensation signal line INIT. The internal compensation circuit CC
sets the gate-source voltage of the driving transistor DR to a
voltage that reflects variation in threshold voltage, so as to
cancel out any brightness variation caused by the threshold voltage
of the driving transistor DR when the organic light-emitting diode
OLED emits light. In this case, the scan line GL1 comprises at
least two scan lines GL1a and GL1b for controlling the switching
transistor SW and the transistors in the internal compensation
circuit CC.
[0043] As shown in (b) of FIG. 3, the subpixel can comprise a
switching transistor SW1, a driving transistor DR, a sensing
transistor SW2, a capacitor Cst, and an organic light-emitting
diode OLED. The sensing transistor SW2 is a transistor that can be
included in the internal compensation circuit CC, and performs a
sensing operation for compensating for the subpixel.
[0044] The switching transistor SW1 serves to supply a data voltage
supplied through the data line DL1 to a first node N1, in response
to a scan signal supplied through the first scan line GL1a. The
sensing transistor SW2 serves to reset or sense a second node N2
situated between the driving transistor DR and the organic
light-emitting diode OLED, in response to a sensing signal supplied
through the second scan line GL1b.
[0045] The structure of the subpixel according to the present
disclosure is not limited to the above, but can vary, including 2T
(transistor)1C (capacitor), 3T1C, 4T2C, 5T2C, 6T2C, and 7T2C.
[0046] Referring to (a) and (b) of FIG. 4, an organic
light-emitting display according to an exemplary embodiment of the
present disclosure comprises a thin-film transistor substrate SUB.
On the thin-film transistor substrate SUB, thin-film transistors T
individually allocated to pixels and organic light-emitting diodes
OLE connected to the thin-film transistors T are placed.
Neighboring pixels PXL can be defined by a bank BN (or pixel
definition layer), and the planar shape of each pixel PXL can be
defined by the bank BN. Thus, the position and shape of the bank BN
can be properly selected so that the pixels PXL have a preset
planar shape.
[0047] The thin-film transistors T can have various structures,
including a bottom-gate structure, a top-gate structure, and a
double-gate structure. That is, each thin-film transistor T can
comprise a semiconductor layer, a gate electrode, and source/drain
electrodes. The semiconductor layer, gate electrode, and
source/drain electrodes can be arranged on different layers, with
at least one insulating layer in between.
[0048] At least one insulating layer can be interposed between the
thin-film transistor T and the organic light-emitting diode OLE.
The insulating layer can comprise a planarization layer made of an
organic material such as photoacryl, polyimide, benzocyclobutene
resin, or acrylate resin. The planarization layer can planarize the
surface of a substrate where the thin-film transistor T and various
signal lines are formed. The insulating layer can further comprise
a passivation layer composed of a silicon oxide film (SiOx), a
silicon nitride film (SiNx), or multiple layers of them, and the
passivation layer can be interposed between the planarization layer
and the thin-film transistor T. The thin-film transistor T and the
organic light-emitting diode OLE can be electrically connected via
a pixel contact hole PH penetrating one or more insulating
layers.
[0049] The organic light-emitting diode OLE comprises first and
second electrode E1 and E2 facing each other, and an organic
compound layer OL interposed between the first electrode E1 and the
second electrode E2. The first electrode E1 can be an anode, and
the second electrode E2 can be a cathode.
[0050] The first electrode E1 can be composed of a single layer or
multiple layers. The first electrode E1 further comprises a
reflective layer to function as a reflective electrode. The
reflective layer can be made of aluminum (Al), copper (Cu), silver
(Ag), nickel (Ni), or an alloy of these elements, preferably, APC
(silver/palladium/copper alloy). In an example, the first electrode
E1 can be formed of triple layers of ITO/Ag/ITO. The first
electrodes E1 can be individually allocated to the pixels--one for
each pixel.
[0051] A bank BN for defining neighboring pixels is located on the
substrate SUB where the first electrodes El are formed. The bank BN
can be made of an organic material such as polyimide,
benzocyclobutene resin, or acrylate resin. The bank BN comprises
apertures for exposing most of the center of the first electrodes
E1.
[0052] Parts of the first electrodes E1 exposed by the bank BN can
be defined as emitting regions. The bank BN can be disposed to
expose the center of the first electrodes E1 but cover the side
edges of the first electrodes E1.
[0053] An organic compound layer OL emitting white light (W) is
formed on the substrate SUB where the bank BN is formed. The
organic compound layer OL is disposed to extend on the thin-film
transistor substrate SUB so as to cover the pixels. The organic
compound layer OL can have a multi-stack structure such as a
two-stack structure. The two-stack structure can comprise a charge
generation layer CGL situated between the first electrode E1 and
the second electrode E2, and a first stack STC1 and a second stack
STC2 that are located under and over the charge generation layer
CGL sandwiched between them. The first stack STC1 and the second
stack STC2 each comprise an emission layer, and can further
comprise at least one of common layers such as a hole injection
layer, a hole transport layer, an electron transport layer, and an
electron injection layer. The emission layer of the first stack
STC1 and the emission layer of the second stack STC2 can comprise
light-emitting materials of different colors.
[0054] In another example, the organic compound layer OL emitting
white light (W) can have a single-stack structure. Each single
stack comprises an emission layer EML, and can further comprise at
least one of common layers such as a hole injection layer HIL, a
hole transport layer HTL, an electron transport layer ETL, and an
electron injection layer EIL.
[0055] The second electrode E2 is formed on the substrate SUB where
the organic compound layer OL is formed. The second electrode E2
can be made of a transparent conductive material such as ITO
(indium tin oxide), IZO (indium zinc oxide), or ZnO (zinc oxide),
or can be made of a thin opaque conductive material such as
magnesium (Mg), calcium (Ca), aluminum (Al), or silver (Ag) and
function as a transmissive electrode. The second electrode E2 can
integrally extend on the thin-film transistor substrate SUB so as
to cover the pixels.
[0056] The organic light-emitting display according to the present
disclosure comprises color filters CF. One color filter CF can be
allocated to each pixel. The color filters CF can comprise red (R),
green (G), and blue (B) color filters that let light of red (R),
green (G), and blue (B) colors pass through. The red (R), green
(G), and blue (B) color filter CF are allocated to the
corresponding red (R), green (G), and blue (B) pixels.
[0057] In an example, the color filters CF can be formed on the
thin-film transistor substrate SUB. To prevent deterioration of the
organic light-emitting diodes OLE due to exposure to the
environment provided in the formation process of the color filters
CF, an encapsulation layer ENC can be sandwiched between the color
filters CF and the organic light-emitting diodes OLE. Moreover, the
encapsulation layer ENC can prevent moisture and/or oxygen from
entering the organic light-emitting diodes OLE. Accordingly, there
is an advantage in that degradation in the lifetime and brightness
of the organic light-emitting diodes OLE can be prevented. The
encapsulation layer ENC can be a stack of at least one inorganic
film and at least one organic film. The inorganic film and the
organic film can alternate with each other. Neighboring color
filters CF can be defined by a black matrix BM formed on the
encapsulation layer ENC (see (a) of FIG. 4).
[0058] In another example, color filters CF can be formed on an
opposing substrate CSUB facing a substrate SUB. The opposing
substrate CSUB can be made of a transparent material to allow the
light emitted from the organic light-emitting diode OLE to pass
through. Neighboring color filters CF can be defined by a black
matrix BM formed on the opposing substrate CSUB (see (b) of FIG.
4).
[0059] Light generated from inside the organic compound layer OL is
emitted in multiple directions. To increase the luminous efficiency
of the organic light-emitting diode OLE, the emitted light needs to
be controlled to travel in a preset direction (hereinafter,
referred to as an orientation direction). That is, a transmissive
electrode and a reflective electrode can be disposed to face each
other with the organic compound layer OL interposed between them,
in order to control the direction of travel of the emitted light.
In the present disclosure, the first electrode E1 can function as
the reflective electrode, and the second electrode E2 can function
as the transmissive electrode.
[0060] Part of the generated light that travels in the orientation
direction passes through the transmissive electrode and is emitted
out of the display device. The direction of another part of the
light is changed to the orientation direction through the
reflective electrode and then sequentially passes through the
transmissive electrode and the color filter CF and is emitted out
of the display device. In this way, the addition of the reflective
electrode allows for changing the direction of travel of light that
does not initially travel in the orientation direction to the
orientation direction, thereby improving light efficiency.
[0061] However, referring further to FIG. 5 which illustrates
problems with the related art, some L1 of the light emitted from
the organic compound layer OL does not pass through the color
filter CF allocated to the corresponding pixel but can travel
toward a neighboring color filter CF. In this case, a color mixing
defect occurs, causing a significant degradation in display
quality, which can be a problem. In contrast, in an exemplary
embodiment of the present disclosure, a black matrix BM can be
included to improve such a color mixing defect. Furthermore, the
cell gap CG or the width of the black matrix BM can be properly
adjusted to effectively improve the color mixing defect using the
black matrix BM.
[0062] However, some L2 of the light emitted from the organic
compound layer OL can be wave-guided toward a neighboring pixel
through total reflection between the interfaces of thin-film layers
formed on the path of light travel, due to differences in
refractive index between the thin-film layers, or can pass through
the surface and inside of the bank BN and be wave-guided toward the
neighboring pixel. The light directed toward a neighboring pixel is
not sent out in the orientation direction, but can travel toward
the neighboring color filter CF or can be reflected off the first
electrode E1 and travel toward the neighboring color filter CF. The
direction of travel of the light L2 can be shifted severely from
the orientation direction, which can be a limitation in blocking
this light L2 using the black matrix BM.
[0063] In a high-resolution display device with a high PPI (pixels
per inch), the pixel size is relatively small, which makes the
color mixing caused by the wave-guided light L2 more problematic.
Accordingly, the exemplary embodiment of the present disclosure
proposes a novel structure for minimizing the aforementioned color
mixing defect.
First Exemplary Embodiment
[0064] FIG. 6 is a cross-sectional view schematically showing an
organic light-emitting display device according to a first
exemplary embodiment of the present disclosure.
[0065] Referring to FIG. 6, an organic light-emitting display
according to the first exemplary embodiment of the present
disclosure comprises a thin-film transistor substrate SUB.
Thin-film transistors T respectively corresponding to the pixels
and organic light-emitting diodes OLE connected to the thin-film
transistors T are placed on the thin-film transistor substrate SUB.
The organic light-emitting diode OLE comprises a first electrode
E1, a second electrode E2, and an organic compound layer OL
interposed between the first electrode E1 and the second electrode
E2.
[0066] Neighboring pixels can be partitioned by a bank BN, and the
planar shape of each pixel PXL can be defined by the bank BN. Thus,
the position and shape of the bank BN can be properly selected in
order to form pixels PXL having a preset planar shape.
[0067] The organic light-emitting display device according to the
first exemplary embodiment of the present disclosure comprises
hollow portions BH formed in the bank BN and light stoppers LS
inserted into the hollow portions BH. A plurality of hollow
portions BH can be formed on the bank BN between neighboring
pixels, and light stoppers LS can be individually inserted into the
hollow portions BH.
[0068] The hollow portions BH can have the shape of a hole that
fully penetrates the entire thickness of the bank BN and exposes
the underlying layer of the bank BN, or can have the shape of a
recess formed by partially recessing the top surface of the bank BN
inward.
[0069] The light stoppers LS are fitted into the hollow portions BH
and protrude toward the color filters CF. Thus, the top surface of
the light stoppers LS can be spaced a preset distance apart from
the top surface of the bank BN. The light stoppers LS can be
correctly aligned to their positions compared to a simple stack
structure, since they are fitted into the hollow portions BH.
[0070] The light stoppers LS can comprise a black material to block
and/or absorb the light incident on the light stoppers LS. In an
example, the light stoppers can comprise one of the following:
carbon black, a mixed dye with a carbon black in it, a black resin,
graphite powder, gravure ink, black spray, and black enamel. In
another example, the light stoppers LS can comprise, but not
limited to, a photoresist formed based on an organic black
material.
[0071] A portion of the light stopper LS that protrudes outward
from the bank BN can be can block and/or absorb the light that
wave-guided between the interfaces of thin-film layers. And/or the
portion of the light stopper LS can be can block and/or absorb the
light traveling through the surface of the bank BN and directed
toward a neighboring color filter CF. A portion of each light
stopper LS that is fitted into the bank BN via the hollow portion
BH can block and/or absorb the light traveling into inside of the
bank BN and directed toward the neighboring color filter CF.
Accordingly, the first exemplary embodiment of the present
disclosure provides an organic light-emitting display device that
improves display quality by significantly reducing color mixing
defects.
[0072] FIG. 7 is a view for explaining the positional relationship
of a light stopper according to an example of the present
disclosure.
[0073] Referring to FIG. 7, the light stopper LS can be selectively
provided at a specific position. That is, the light stopper LS does
not have to be placed between each neighboring pixel PXL in all
areas but can be selectively provided between neighboring pixels
PXL at a position where it is needed.
[0074] If the neighboring pixels PXL are pixels that emit light of
the same color, a color mixing defect between the neighboring
pixels PXL can not be a problem. Taking this into consideration, in
the first exemplary embodiment, whether to place the light stopper
LS between neighboring pixels PXL or not can be determined based on
which color is allocated to the neighboring pixels PXL.
[0075] For example, if a first pixel PXL emits light of a first
color, a pixel PXL neighboring the first pixel PXL in a first
direction can be a second pixel PXL2 that emits light of a second
color, and a pixel PXL neighboring the first pixel PXL1 in a second
direction can be a third pixel PXL3 that emits light of the first
color. Here, the light stopper LS can be formed between the first
and second pixels PXL1 and PXL2 which emit light of different
colors, and the light stopper LS can not be formed between the
first and third pixels PXL1 and PXL3 which emit light of the same
color. This offers the advantage of having a degree of freedom of
the process, since the light stopper LS is formed selectively in
areas where it is needed. Another advantage is that the bank BN is
made relatively narrow in areas where the light stopper LS is not
formed, thus resulting in an aperture ratio corresponding to the
width of the bank BN.
[0076] FIGS. 8 and 9 are views for explaining another advantage of
the first exemplary embodiment of the present disclosure.
[0077] In high-resolution display devices which have a relatively
small pixel pitch, light is emitted from unwanted pixels PXL due to
a leakage current through the organic compound layer OL, and this
can lead to a color mixing defect between neighboring pixels. For
example, although neighboring pixels PXL are defined by a pixel
definition layer such as a bank BN and spaced by a predetermined
pitch, higher-resolution display devices have a much smaller pixel
pitch, and therefore the color mixing defect caused by leakage
current will occur more often. At least one layer that makes up the
organic compound layer OL and has high conductivity--for example,
the charge generation layer in a multi-stack structure--can serve
as a leakage current flow path, which can be a problem.
[0078] Referring to FIG. 8, in the first exemplary embodiment of
the present disclosure, light stoppers LS protruding further than
the top surface of the bank BN are provided, and the organic
compound layer OL is formed over the light stoppers LS, thereby
providing a sufficiently long path of leakage current that can flow
to neighboring pixels. That is, a relatively long flow path of
leakage current can be provided, because a layer (e.g., charge
generation layer) forming the flow path of leakage current is
deposited along the shape of the surface of the light stoppers LS.
Accordingly, the first exemplary embodiment can effectively
eliminate leakage current and therefore avoid a significant
degradation in display characteristics caused by the emission of
light from unwanted pixels.
[0079] Referring to (a) and (b) of FIG. 9, in the first exemplary
embodiment of the present disclosure, the organic compound layer OL
comprising a layer serving as the path of leakage current can be
separated in a certain region, in order to effectively eliminate
leakage current. That is, as shown in the drawing, the organic
compound layer OL can be physically separated in at least one
region due to the stepped portion formed by the light stopper LS
and the bank BN. Accordingly, the first exemplary embodiment of the
present disclosure has the advantage of further minimizing the
color mixing defect caused by leakage current, since the path of
leakage current in at least one region can be blocked.
[0080] In this case, the second electrode E2 is formed in an
integrated fashion so as to cover all pixels and supply low-level
voltage to the individual pixels. It means that some pixels can not
be driven if the second electrode E2 is physically separated into a
plurality of parts. Thus, in the first exemplary embodiment of the
present disclosure, the process method and material can be
controlled in such a way that the organic compound layer OL is
separated but the second electrode E2 is not separated (see (a) of
FIG. 9).
[0081] Alternatively, in the first exemplary embodiment of the
present disclosure, the organic compound layer OL and second
electrode E2 at a specific position can be selectively separated by
selectively placing the light stopper LS at the specific position.
In this case, the path of leakage current can be blocked since the
light stopper LS at the specific position is selectively separated.
Also, the second electrode E2 at the specific position can be
selectively separated, thereby preventing the pixel at the specific
position from not working (see (b) of FIG. 9).
Second Exemplary Embodiment
[0082] FIG. 10 is a cross-sectional view schematically showing an
organic light-emitting display device according to a second
exemplary embodiment of the present disclosure.
[0083] Referring to FIG. 10, an organic light-emitting display
device according to the second exemplary embodiment of the present
disclosure comprises a thin-film transistor substrate SUB.
Thin-film transistors T respectively corresponding to the pixels
and organic light-emitting diodes OLE connected to the thin-film
transistors T are placed on the thin-film transistor substrate SUB.
The organic light-emitting diode OLE comprises a first electrode
E1, a second electrode E2, and an organic compound layer OL
interposed between the first electrode E1 and the second electrode
E2.
[0084] Neighboring pixels can be defined by a bank BN, and the
planar shape of each pixel PXL can be defined by the bank BN. Thus,
the position and shape of the bank BN can be properly selected in
order to form pixels PXL having a preset planar shape.
[0085] The organic light-emitting display device according to the
second exemplary embodiment of the present disclosure comprises
hollow portions BH formed in the bank BN, light stoppers LS
inserted into the hollow portions BH, and barriers BR wrapping
around the light stoppers LS.
[0086] The hollow portions BH can have the shape of a hole that
fully penetrates the entire thickness of the bank BN and exposes
the underlying layer of the bank BN, or can have the shape of a
recess formed by partially recessing the top surface of the bank BN
inward.
[0087] The light stoppers LS are fitted into the hollow portions BH
and protrude toward the color filters CF. Thus, the top surface of
the light stoppers LS can be spaced a preset distance apart from
the top surface of the bank BN. The light stoppers LS can be
correctly aligned to their positions compared to a simple stack
structure, since they are fitted into the hollow portions BH.
[0088] The light stoppers LS can comprise a black material to block
and/or absorb the light incident on the light stoppers LS. In an
example, the light stoppers can comprise one of the following:
carbon black, a mixed dye with a carbon black in it, a black resin,
graphite powder, gravure ink, black spray, and black enamel. In
another example, the light stoppers LS can comprise, but not
limited to, a photoresist formed based on an organic black
material.
[0089] A portion of each light stopper LS that protrudes outward
from the bank BN can be wave-guided between the interfaces of
thin-film layers, or can block and/or absorb the light wave-guided
through the surface and inside of the bank BN and directed toward a
neighboring color filter CF. A portion of each light stopper LS
that is fitted into the bank BN via the hollow portion BH can block
and/or absorb the light wave-guided into the bank BN and directed
toward the neighboring color filter CF. Accordingly, the second
exemplary embodiment of the present disclosure provides an organic
light-emitting display device that improves display quality by
significantly reducing color mixing defects.
[0090] Meanwhile, the organic compound layer OL can be deteriorated
due to an out-gas produced from a pigment forming the light
stoppers LS. Thus, the organic light-emitting display device
according to the second exemplary embodiment of the present
disclosure can further comprise barriers BR surrounding the light
stoppers LS in order to prevent deterioration of the organic
compound layer OL caused by an out-gas. The barriers BR can be
disposed to fully wrap around the light stoppers LS. The barriers
BR can be made of an inorganic material such as a silicon oxide
film (SiOx) or a silicon nitride film (SiNx), and can be composed
of a single layer or multiple layers of the inorganic material.
[0091] Accordingly, the second exemplary embodiment of the present
disclosure can prevent an out-gas produced from the light stoppers
LS from entering the organic compound layer OL by having barriers
BR fully covering the light stoppers LS. Therefore, the second
exemplary embodiment of the present disclosure has the advantage of
ensuring device reliability by preventing deterioration of the
organic light-emitting diodes caused by the out-gas.
[0092] FIGS. 11A to 11D are views chronologically showing an
example of a barrier formation method according to an example of
the present disclosure.
[0093] Referring to FIG. 11A, at least one hollow portion BH is
formed on the bank BN. As mentioned previously, the hollow portion
BH can be formed through the entire or part of the thickness of the
bank B.
[0094] Referring to FIG. 11B, a first inorganic material IM1 is
applied onto the bank BN where the hollow portion BH is formed.
Afterwards, the first inorganic material IM1 can be patterned so
that the first inorganic material IM1 is left at least within the
hollow portion BH. Although the figure illustrates an example in
which the first inorganic material IM1 is left only within the
hollow portion BH, the present disclosure is not limited to this
example and the first inorganic material IM1 can be patterned to
such an extent that it is not left in the emitting region (e.g.,
first electrode E1--see FIG. 10).
[0095] Referring to FIG. 11C, a light stopper LS is formed within
the hollow portion BH in such a way that at least part of it is
fitted into the hollow portion BH. The bottom of the light stopper
LS within the hollow portion BH is disposed to be surrounded by the
first inorganic material IM1.
[0096] Referring to FIG. 11D, a second inorganic material IM2 is
applied onto the bank BN where the light stopper LS is formed.
Afterwards, the second inorganic material IM2 can be patterned so
that the second inorganic material IM2 is left at least within the
hollow portion BH. The second inorganic material IM2 can be
patterned to such an extent that it is not left in the emitting
region (e.g., first electrode E1--see FIG. 10).
[0097] The remaining first inorganic material IM1 and second
inorganic material IM2 can be disposed to fully wrap around the
light stoppers LS and serve as a barrier BR. That is, the barrier
BR can be divided into a first portion containing the first
inorganic material IM1 and a second portion containing the second
inorganic material IM2. The first portion and the second portion
can contain the same material or different materials. The second
exemplary embodiment of the present disclosure can improve device
reliability by effectively eliminating the problem of an out-gas
produced from a pigment forming the light stopper LS.
[0098] Through the above description, those skilled in the art will
appreciate that various modifications and changes are possible,
without departing from the scope and spirit of the disclosure.
Therefore, the technical scope of the present disclosure should be
defined by the appended claims rather than the detailed description
of the specification.
* * * * *